Technical Field
The technology relates to touch-sensitive capacitive matrices that are used to enable touch control of electronic devices. The technology further relates to cancelling parasitic capacitance effects in such touch-sensitive capacitive matrices.
Discussion of the Related Art
A touch-sensitive capacitive matrix may be incorporated into a pad or tablet-like element, and can detect an object in contact with or in proximity to the pad. The element may be part of an electronic device that includes at least one processor configured to operate the device. Because the capacitive sensors of a capacitive matrix are disposed in a two-dimensional array in the pad or tablet-like element, the location on the on the element at which the object touches or is in proximity to the element can be ascertained.
Touch-sensitive capacitive matrices have been incorporated into display screens of smart electronic apparatuses (e.g., into displays of smart phones, computers, net books, personal digital assistants, tablets, etc.) to provide a convenient method for users to interact with the apparatuses. Such a display is sometimes referred to as a “touch screen.” The display area may be covered with a touch-sensitive capacitive matrix that can detect a user's touch by way of a finger or stylus, for example. A touch screen may enable various types of user input, such as touch selection of items on the screen, alphanumeric input via a displayed virtual keypad, scrolling operation, and scaling operations (e.g., zoom in/zoom out). Touch screens may also be used to detect various parameters of the user's touch, such as one or more locations of contact, size of a contact area, and duration of contact. The terms “touch” and “contact” when used herein to refer to touch control is meant to include physical contact as well as proximal positioning of a controlling object (e.g., a finger, a stylus) with respect to a touch-sensitive capacitive matrix. It will be understood that physical contact and proximal position may each affect a response in a touch-sensitive capacitive matrix.
One example of an electronic device 100 that may include a touch-sensitive capacitive matrix is shown in FIG. 1. The device shown in FIG. 1 may be a smart phone, for example, and include a display screen 110 and one or more push-style control buttons 120. The display screen may be configured as a touch screen. Inside a casing 105 may be electrical circuitry, hardware, at least one processor, memory storing machine-readable instructions operable on the at least one processor, and a power source (e.g., a rechargeable battery). The device 100 may further include wireless communication electronics, one or more motion-sensors, GPS circuitry, and a magnetometer.